The present invention relates to an improvement of a variable valve operating apparatus for an internal combustion engine which variably controls the lift and open duration of engine valves, i.e., intake and/or exhaust valves, depending on engine operating conditions.
Japanese Patent Application First Publication No. 2002-371816 discloses a variable valve operating apparatus for an internal combustion engine, which includes a bifurcated rocker arm disposed above a cylinder head with two intake valves per cylinder. The rocker arm with a roller includes one end portion pivotal about a pivot and the other two branched end portions which are contacted with stem ends of the intake valves, respectively. A control shaft is rotatably disposed above the rocker arm. A first intervening arm is pivotally supported on the control shaft and drives the roller of the rocker arm. A second intervening arm is pivotally supported on a projecting portion integrally formed with the control shaft. A drive cam on a cam shaft urges the second intervening arm onto the first intervening arm to thereby cause the pivotal motion of the first intervening arm. By rotating the control shaft and the projecting portion in a relatively small angular range, the pivotal motion of the first intervening arm by the drive cam is controlled so that the lift and open duration of the intake valves through the rocker arm are varied.